Image forming apparatuses using a liquid ejection head (i.e., droplet ejection head) such as ink droplet ejection heads have been used for printers, copiers, plotters and multifunctional products having two or more of the printing, facsimileing, copying and plotting functions. Specific examples of such image forming apparatuses include inkjet recording apparatuses.
With respect to the liquid ejection head, liquid ejection heads using a piezoelectric actuator, a thermal actuator or an electrostatic actuator as a pressure generating device (i.e., actuator) are known.
The liquid ejection property of a liquid ejection head is largely affected by the condition of the droplet ejection surface (i.e., nozzle forming surface) of the nozzle substrate of the liquid ejection head. For example, when a liquid adheres to the peripheral part of a nozzle of a liquid ejection head, the droplet ejection direction of the liquid ejection head varies. In addition, if the liquid is solidified, the diameter of the nozzle narrows, and thereby a problem such that the amount (size) of a droplet ejected from the liquid ejection head is decreased or the droplet ejection speed is varied is caused. In attempting to prevent occurrence of such a problem, i.e., to enhance the droplet ejection property of a liquid ejection head, a liquid repellent layer (such as water repellent layer and ink repellent layer) is typically formed on the surface of the droplet ejection surface of the liquid ejection head.
JP-2009-214338-A discloses a droplet ejection head having a structure such that a surface treatment layer (intermediate layer) such as a SiO2 layer is formed on an ejection surface of the nozzle substrate of the droplet ejection head as a base layer, and an organic liquid repellent layer such as a resin layer is formed on the base layer.
In addition, JP-2004-351923-A discloses a liquid ejection head having a structure such that a plasma polymerization layer of a silicone material is formed on an ejection surface of a nozzle substrate of the liquid ejection head as a base layer, and a liquid repellent layer such as a molecular layer of a polymerized metal alkoxide is formed on the base layer. In this head, materials including one of SiO2, ZnO, NiO, SnO2, Al2O3 ZrO2, copper oxide, silver oxide, chromium oxide, and iron oxide can be used for the base layer other than the plasma polymerization layer of a silicone material.